Veterinary Services

DNA Test for Copper Toxicosis in Bedlington Terriers

The Animal Health Test announces an updated DNA test for copper toxicosis in Bedlington Terriers. The research underlying this test was carried out jointly by a team led by Dr Mike Boursnell at the Animal Health Trust and at the University of Nottingham in the laboratory of Dr Paul Jones (Masterfoods Ltd.). This basic science was developed into a diagnostic test at the Animal Health Trust with funding from the American Kennel Club Canine Health Foundation.

Copper toxicosis is an hereditary disease in which failure of the liver to expel dietary copper leads to a build-up of this toxic metal causing illness and death. It is inherited as an autosomal recessive trait. As such, two copies of the defective gene, one inherited from each parent, need to be present before an individual displays clinical signs. Dogs with one copy of the defective gene and one copy of the normal gene (carriers), will not show clinical signs, but will be able to transmit the defective gene to their offspring. A reservoir of symptom-less carriers exists in the population and when two carriers are bred, affected dogs may be thrown up in the litter. Unlike liver biopsy, DNA testing has the potential to pick out carriers as well as affected dogs so that all dogs bearing the defective gene can now be identified and the disease gene eventually eradicated from the population.

The previous DNA test detected changes in a DNA marker. Recent research has identified the mutation as a massive deletion of part of the DNA of a gene called COMMD1. Studies at the AHT and the University of Nottingham have now identified the limits of this deletion, enabling us to devise a new diagnostic test. This research has been published as. "Characterisation of the COMMD1 (MURR1) mutation causing copper toxicosis in Bedlington terriers" (2005). O. P. Forman, M.E.G. Boursnell, B. J. Dunmore, N. Stendall, B. van der Sluis, N. Fretwell, C. Jones, C. Wijmenga, J. Rothuizen, B. A. van Oost, N. G. Holmes, M. M. Binns and P. Jones. Animal Genetics Vol 36 pp497-501.

The results from the new test will be definitive for this mutation and will identify the dog as CLEAR of, a CARRIER of or AFFECTED by copper toxicosis caused by the deletion in the gene COMMD1.

An explanation of terms used will be provided as follows :-

CLEAR: the dog has 2 copies of the normal gene and will neither develop copper toxicosis caused by the known deletion in the COMMD1 gene, nor pass this mutation to its offspring.

CARRIER: the dog has one copy of the normal gene and one copy of the mutated COMMD1 gene. It will not develop copper toxicosis caused by this mutation but if bred from will pass on the mutation to (on average) 50% of its offspring.

AFFECTED: the dog has 2 copies of the mutant gene and has copper toxicosis.

This test is an extension of the previous test offered for this disease, which used the DNA marker C04107. The new test is not subject to the element of doubt, which existed in the old test. However, results from the old test are still valid. The Table below compares results from the old test with the results from the new COMMD1 deletion test.

C04107 Test

COMMD1 deletion test

1-1

clear

1-2

carrier or clear

1-3

clear

2-2

affected or carrier or clear

2-3

carrier or clear

Dogs with 1-2 status are most likely to be carriers, however, there is a small possibility that they could be clear of the disease gene. For dogs of 2-2 status, there is a small possibility that they could be carriers - and even, very rarely, clear of the disease gene.

Whilst the test is definitive for this mutation, it is possible that there are other genetic causes of copper toxicosis in Bedlingtons, as yet unidentified, which will not be detected by this test.

The DNA marker test using C04107 is still available, but by special arrangement only.

Samples submitted should be cheek swabs (a non-invasive sampling method) obtainable only from the Animal Health Trust. Kits for taking cheek swabs are available through our web-site http://www.aht.org.uk. Further information can be obtained by e-mailing dnatesting@aht.org.uk

The Animal Health Trust is a veterinary charity, based in Suffolk, which offers clinical referral services and diagnostic testing for horses, dogs and cats in East Anglia, across the UK and internationally. Through its research programmes it develops new diagnostic tests, treatments and vaccines to help thousands of animals.